1. Technical Field
This invention relates to electrostatographic cleaning apparatus and, more particularly, to a cleaning blade for use in such apparatus, and to a method for making such a blade. The blades described herein are adapted to load and seal against the surface being cleaned in a substantially precise manner despite spatial variabilities in the mounting of the blade, the straightness of the cleaning edge, or that of the surface being cleaned.
2. Background Art
Electrostatographic process apparatus which, for example, produce or reproduce toned images on selected substrates by employing electrostatic charges and toner particles on an insulated photoconductive surface, typically operate through a sequence of currently well known steps. These steps include (1) charging of the insulated photoconductive surface with electrostatic charges, (2) forming a latent image electrostatically on such surface by selectively discharging areas on such surface, (3) developing the electrostatic image so formed with particles of toner, (4) transferring the toned image to a suitable substrate for fusing thereon to form a permanent record, and (5) cleaning by removing residual toner and/or other particles from the photoconductive surface in preparation for similarly producing another image.
The quality of the images produced by such apparatus depends significantly on the ability to clean the photoconductive surface before it is reused. Several types of cleaning mechanisms, including blade-type cleaners as disclosed, for example, in U.S. Pat. No. 4,789,432, issued Dec. 6, 1988 in the name Goodnow et al. Typically, such a cleaning blade device has a sharp edge at one end for cleaning, and is supported by suitable means as a cantilevered member at its other end. The length of the cleaning edge, and hence of the first end, is determined ordinarily by the width of the surface to be cleaned.
In electrostatographic apparatus such as a copier or printer including an image-bearing surface, the range of a loading force per unit length that can be applied for loading the cleaning edge of such a blade against the image-bearing surface is limited, for example to 0.1 to 0.2 lb./in. in order not to damage such image-bearing surface being cleaned. Conventionally, therefore (given a load force per unit length value within such a limited range), the material for the cantilevered or free extension width of the blade, as well as its thickness, are then selected and formed so as to achieve a desired deflection or particular load value of the blade against the surface being cleaned. Another conventional way or method for making a cleaning blade is by trial and error of various blades of varying thicknesses and widths until one is formed that is believed will work. It is then selected and loaded against the surface being cleaned such that it has a desired load force per unit length of its cleaning edge, as well as a desired deflection thereof relative to the surface. The desired force load per unit length must be high enough in order to result in an effective sealing of the cleaning edge against such surface, but not so high as to damage such surface. Precision of the actual force loading and actual sealing achieved relative to such desired values is, therefore, important.
Unfortunately, however, it has been found that for a conventional trial and error selected blade that is loaded so as to have, for example, a 0.1 lb./in. load force per unit length, the actual load force per unit length experienced across the length of the cleaning edge can vary substantially, for example by as much as 60%. This can be due, for example, to a spatial variability of as little as 0.003 of an inch in the straightness of the cleaning edge, in that of the surface being cleaned, and/or in runout or eccentricity of the surface being cleaned. Such a substantial variation of the actual loading force per unit length across the length of the cleaning edge can undesirably result in ineffective sealing and cleaning at the low end, and in significant damage to the image-bearing surface at the high end.